Figure 1.

Schematic diagram of the nucleoskeleton and its relationships to the nuclear envelope and cytoskeleton. The proposed major components of the vertebrate nucleoskeleton are illustrated. The lamina comprises polymers of A- and B-type lamins. A fraction of lamins are also present in the nuclear interior, possibly associated with chromatin, but not demonstrably in a polymerized form. Short filaments of actin are illustrated, although monomeric actin might also be present. Nuclear spectrin is indicated as associated primarily with the nuclear envelope/lamina. A nuclear isoform of titin also occurs in most eukaryotic cell nuclei and associates with both chromosomes and the lamina. Pore-linked filaments (PLFs) associated with nuclear pore complexes (NPCs) might interact with chromatin and other nucleoskeletal components. The nucleoskeleton is linked to the cytoplasmic skeletal components through LINC (links the nucleoskeleton and cytoskeleton) complexes comprising SUN (Sad1p–UNC-84)-domain proteins and nesprins (nuclear envelope spectrin-repeat proteins). NM, nuclear membrane (nuclear envelope).